For the BVM 91, that I am currently using, I use Wildcat 10% and the MC-09. Very reliable setup, the current plug has 7 flight and it almost looks like new.

For my OS91 I use wildcat 5% and the same plug, also very reliable. I have 30 flight on the plane and I am on the second plug.

On both engines I prefer to set up the neddle on the rich side (not one lean run yet).

Regards
Eduardo